1. Field of the Invention
The present invention relates to an intraventricular multielectrode cardiac mapping probe and to a method of using same for endocardial mapping of a heart chamber, such as a ventricle.
2. Description of the Prior Art
Cardiac mapping is a method by which potentials recorded directly from the heart are spatially depicted as a function of time in an integrated manner. Electrodes are utilized for recording potentials at different positions on the wall surface of a heart chamber, such as the endocardial wall of a ventricle, so that various and important electrophysiological variables can be identified from the cardiac recordings. Such variables include local activation times, waveform analyses, and potential distribution during depolarization and repolarization. Cardiac mapping is very important in locating abnormal foci in the heart and the mapping probe may even be utilized in destroying such foci.
Information on techniques of cardiac mapping are disclosed in numerous articles written about cardiac mapping and one very informative article containing much background information on cardiac mapping is "Techniques of Intraoperative Electrophysiologic Mapping" by John J. Gallagher, et al. which appeared in the January, 1982 issue of "The American Journal of Cardiology", Volume 49, pages 221-240.
Cardiac mapping can be performed in an epicardial manner, that is to say, on the exterior wall surface of the heart, and in an endocardial manner, that is, within an interior chamber wall or endocardial wall in the heart.
Mapping often requires a difficult and risky surgical procedure where an incision is made through the chest wall for epicardial mapping, and further, through the wall of the heart for endocardial mapping so that a sensing probe (or electrode) can be positioned within the heart chamber at different positions on the wall of the heart chamber.
It will be appreciated that this can be an involved and risky procedure, and accordingly, it is desirable to provide an endocardial procedure that does not require cutting through the chest wall and through the heart wall while still being able to make endocardial measurements of different potentials on an interior heart chamber wall for creating a potential distribution map.
Endocardial mapping is preferred since with epicardial mapping it is not certain that epicardial conduction pathway mapping represents "true" conduction pathways. Further, epicardial mapping is a very traumatic procedure.
Accordingly, limited invasive endocardial mapping is preferred and one way of carrying out such mapping has been with multiple electrodes arranged along a single axis on one lead.
A number of devices have been proposed which have multiple electrodes and which can be inserted through a vein or other passageway into a chamber for mapping potentials within the chamber, for sensing and/or for stimulating. Examples of these previous probes and their methods of use are disclosed in the following U.S. Patents:
______________________________________ U.S. PAT. NO. PATENTEE ______________________________________ 3,326,207 Egan 3,825,015 Berkovits 3,903,897 Woollons et al. 3,995,623 Blake et al. 4,172,451 Kline ______________________________________
The Egan U.S. Pat. No. 3,326,207 merely discloses an electrocardiac instrument for testing unborn infants, which instrument includes a balloon on which electrodes are positioned and which can be inserted into the uterus and positioned adjacent a fetus for recording various potentials once the balloon is inflated.
The Berkovits U.S. Pat. No. 3,825,015 discloses a single catheter for atrial and ventricular stimulation where the distal end portion of the catheter has a number of ring electrodes mounted thereon which can be used for sensing potentials within a heart chamber such as in the atrium or in the ventricle.
The Woollons et al U.S. Pat. No. 3,903,897 discloses a cardiac pacer having several ventricular poles or electrodes at a distal end of a pacing lead and several atrial poles spaced a short distance behind the ventricular poles. The atrial poles are, of course, utilized for sensing potentials within the atrium.
The Blake et al U.S. Pat. No. 3,995,623 discloses a multipurpose flow-directed catheter which has a number of ring electrodes thereon for sensing various potentials within a ventricle and within an atrium.
The Kline U.S. Pat. No. 4,172,451 discloses an intracardiac electrode and a method for manufacturing same. The electrode comprises an outer flexible tube containing a plurality of wire leads which extend to perforations in the distal end of a tube forming part of the electrode. The wire lead ends form electrodes which can be utilized for sensing potentials within a heart chamber and particularly for receiving and transmitting electric impulses from different points on a heart wall to a recording and/or information storage unit for direct observation or subsequent analysis.
Except for the balloon structure shown in the Egan U.S. Pat. No. 3,326,207, all of the above referred to patents only disclose elongate, finger-like, lead body distal end portions which have electrodes thereon, and do not provide any form of probe which can be manipulated to form an elliptical envelope whereby electrodes on wire assemblies forming the elliptical envelope can measure various potentials within a heart chamber as provided in the cardiac mapping probe of the present invention.
However, it has been known in the non-analogous art of devices for clearing blood clots to provide an assembly of expandable wires for clearing a blood clot, which expandable wires are inserted into a vein or artery in a generally straight configuration and then are caused to expand outwardly to engage side walls of the vein. Such a non-analogous blood clot filter assembly is disclosed in U.S. Pat. No. 4,425,908.
Also it has been proposed in non-analogous U.S. Pat. No. 4,432,369 to provide an electromagnetic sensor having three electrodes positioned within an elliptical frame which can be inserted in a vein. A generator of a magnetic field is then utilized for measuring signals from the electrodes in this non-analogous electromaganetic sensor, such signals being indicative of a biological condition such as (a) fluid flow in a vein or artery, (b) an esophageal muscular condition or (c) the diameter of a blood vessel.
As will be described in greater detail hereinafter, the intraventricular multielectrode cardiac mapping probe of the present invention differs from the various devices disclosed and described in the patents referred to above by providing at least one, and preferably a plurality, e.g. four, wire assemblies which are movable within a catheter from a position where distal end portions of the wire assemblies are retracted within the catheter and an extended position where the distal end portions of the wire assemblies are extended within a heart chamber and where they are caused to move outwardly to form a generally elliptical envelope so that a plurality of sleeve electrodes, spaced apart on each wire assembly, can contact points on an endocardial wall of a heart chamber, such as an atrium or a ventricle, for making potential measurements at those points. This probe construction provides for electrodes arranged in three dimensions and for a larger number of sensing electrodes than are provided in the prior devices where electrodes are mounted on a single axis.